A simplified answer.
In preferences -> network -> network port configuration; is a list of of ports for the "location" (typically "Automatic")
OS X searches down the list from the top. So if you have Ethernet first and say airport second, modem third, it tries to connect with ethernet first, if no luck goto airport etc.
Now if you want to use Ethernet with DHCP at work and Ethernet with static IP at home, you create a new location and a new list of network ports.
So ... if you use DHCP only then pick the order of search and OS X will sort out your connections. Like one user's experience in this list. (you might be able to to static ip this way aswell ?)
or if you want to use DHCP and static at different locations, then set them up and use the Location menu from the Apple menu.
I hope this helps.
In preferences -> network -> network port configuration; is a list of of ports for the "location" (typically "Automatic")
OS X searches down the list from the top. So if you have Ethernet first and say airport second, modem third, it tries to connect with ethernet first, if no luck goto airport etc.
Now if you want to use Ethernet with DHCP at work and Ethernet with static IP at home, you create a new location and a new list of network ports.
So ... if you use DHCP only then pick the order of search and OS X will sort out your connections. Like one user's experience in this list. (you might be able to to static ip this way aswell ?)
or if you want to use DHCP and static at different locations, then set them up and use the Location menu from the Apple menu.
I hope this helps.